The model for entropic elasticity of a single chain as shown in previous section, predicts the force developed in the chains a function of \(j\) , the number of statistical segment, in the chains. This model was the precursor for lots of other models for the elasticity of polymer networks. In these models, each strand between two crosslink of the network is assumed to follow the entropic elasticity model as described above. Treloar [1]}, [2]} and Wang et al.[3]} proposed the first micromechanical models for rubber elasticity at small deformations using Gaussian statistics. Further developments were based on the Langevin statistics [4]}, [5]} and took into account the finite extensibility of the strands. Due to the complexity of the Langevin statistics, simplified geometric models were proposed for rubber internal structure [6]}, such as tetrahedral model [7]}, three chain model [8]}, and eight-chain model [9]}.
